1. Field
Apparatuses and methods consistent with exemplary embodiments relate to an optical modulator unit, an optical modulator including the optical modulator unit, and a method of fabricating the optical modulator, and more particularly, to a transmissive-type optical modulator unit which transmits infrared rays, an optical modulator including the transmissive type optical modulator unit, and a method of fabricating the optical modulator.
2. Description of the Related Art
A method of measuring distances from a large number of points on a surface of a subject is used in a three dimensional (3D) image acquisition apparatus such as a 3D camera. Time-of-flight (TOF) methods have been introduced to obtain more accurate distance information about a subject. A phase delay measurement method that is one TOF method that uses external modulation (EM) that is favorable for obtaining a distance image with a high resolution. A gallium arsenide (GaAs) semiconductor-based optical modulator, which is easy to implement, has a small size, and may be driven with a low voltage, has been proposed to embody the EM. The GaAs semiconductor-based optical modulator is an optical modulator in which a multiple quantum well (MQW) is disposed between a P-type electrode and an N-type electrode, and uses a phenomenon whereby light is absorbed into the MQW when a reverse bias voltage is applied to both electrodes. The GaAs semiconductor-based optical modulator may be driven at high speed, has a comparatively low driving voltage, and has a large reflectivity difference between a turn-on state and a turn-off state, that is, a large contrast ratio. However, the GaAs semiconductor-based optical modulator has low transmittance with respect to infrared rays.